Titanium nitride (TiN) is a technologically important transition metal nitride. Hoffman, Polyhedron, 13, 1169 (1994). It is a better electrical conductor than is titanium metal and its optical properties resemble those of gold. Toth, Transition Metal Carbides and Nitrides, J. L. Margrave, ed., vol. 7, Academic Press, New York (1971). Titanium nitride is also harder than all elemental metals and sapphire and almost as hard as diamond, having a melting point of about 3000.degree. C. Additionally, TiN is a low temperature superconductor.
TiN films have many potential applications because of their unique combination of properties. Fix et al., Chem. Mater., 5, 614 (1993). They are used, for example, as wear-resistant, friction-reducing coatings on machine tools and as gold-colored decorative coatings. Their optical properties also make them useful as wavelength selective transparent films, and in particular as solar control coatings on windows in warm weather climates. In microelectric devices, TiN films can be used as low resistance contacts, and as diffusion barriers in interconnect metallization schemes.
TiN, as well as other inorganic thin films such as Ta.sub.2 O.sub.5 and AlN, are commonly prepared by chemical vapor deposition (CVD). In CVD, a heat decomposable volatile compound (often an organometallic compound), which may be called the precursor, is contacted with a substrate which has been heated to a temperature above the decomposition temperature of the compound. A coating forms on the substrate which may be a metal, metal mixture or alloy, ceramic, metal compound or mixture thereof, depending on the choice of precursor and reaction conditions. Optionally, a reactant gas is employed to adjust the composition of the final coating. The desirable characteristics of CVD as a thin film formation method include its ability to produce a thin film with good step coverage on a substrate having projections, the ability to readily control the composition of the thin film, and the ability to form a thin film without contamination of, or damage to, the substrate.
However, known CVD processes for manufacturing TiN films, Ta.sub.2 O.sub.5 films, and films comprising other metals, suffer many limitations, primarily due to the precursors employed. For example, although CVD employing metalorganic precursors to produce TiN and Ta.sub.2 O.sub.5 films is a feasible process, it is not optimal, since the known precursors (e.g., dialkylamino-derivatives of titanium such as Ti(NR.sub.2).sub.4 !, and Ta(OEt).sub.5, respectively) are either insufficiently volatile or react too easily with small molecules in the gas phase. The latter is an issue, for example, when ammonia is desired as a co-reactant in a deposition process. Therefore, a need exists for an improved precursor to be used in a CVD process for manufacturing films comprising metals.